Connector plate



April 1968 w. R. MCALPINE 3,377,905 7 2 Sheets-Sheet 1 a1 Filed April 2,1965 FIG! INVENTOR. WILLIAM R. MQALP/NE ATTORNEYS v April 16, 1968 w.R.. MCALPINE CONNECTOR PLATE Original Filed Aprii 2, 1965 2 [3A /IOA 2Sheets-Sheet 2 FIGIO INVENTOR. WILLIAM R. MQALPINE ATTORNEYS UnitedStates Patent 1 Claim. (Cl. 85-13) ABSTRACT OF THE DISCLOSURE A metallicconnector plate for joining wooden members which presents a multiplicityof teeth extending transversely outwardly from the plate. Each. toothhas a base portion and a tip portion of substantially lesser width thanthe base portion. The opposed edges of each portion are parallel withone edge of the tip portion being a continuation of one edge of the baseportion. These teeth may be oriented in rows parallel to the joinderline of the wooden member joined thereby with a predetermined number ofteeth per row for selective utilization of the tensile strength of theplate itself.

This application is a continuation of application Ser. No. 444,972,filed Apr. 2, 1965, and now abandoned.

The present invention relates generally to connector plates forconnecting wooden members together at a joint. More particularly, thepresent invention relates to connector plates having a plurality ofteeth punched therefrom and extending outwardly from the plate to permitthem to be pressed into the wood of the members to be connected.Specifically, the present invention relates to particularly shaped teethfor such connector plates as well as the particular orientation of theteeth with respect to the joint.

Toothed connector plates are particularly adapted for connecting woodenstructural members at their joints. The ultimate strength of such aconnector plate is determined by whichever is the lesser of the threestrength factors a connector plate must possess.

One of the three factors is the tensile strength of the plate itselfthatis, the strength of the plate to resist a tensile force applied acrossthe joinder line of the wooden members connected thereby.

A second factor is the shear strength of the plate. The shear strengthis measured by the aggregate shear strength of the teeth across theirbases parallel to the plate.

The third factor is the holding power of the teeth. That is, theresistance offered by the teeth against extraction from the woodenstructural members into which they are embedded.

It should thus be readily apparent that the ultimate strength of theconnectorplate is controlled by the upper limit of the weakest of theaforementioned three factors. Proper, and FHA approved, designprocedures demand that the design strength value for a connector plateequal 67% of the yield strength or 33% of the ultimate strength,whichever is lower. The yield strength, often referred to as the slippoint, is defined as the load required to cause a separation of thestructural members at the joinder line amounting to 0.015".

The early constructions of connector plates were limited in designstrength by the holding power of the teeth. Further improvements intooth construction increased the holding power to such an extent thatthe tensile strength of the plate became the controlling factor inarriving at a design value and with this the yield strength became thecontrolling design criteria.

To the truss fabricator, or man who uses connector 3,377,905 PatentedApr. 16, 1968 plates to join together wooden structural members, twoadditional considerations are of prime importance. While he requires themaximum strength in the connector plate, he must obtain it from a platewhich can be driven into connecting engagement wtih the wood withminimum driving pressure. Moreover, the plate must be as readily usablewith soft or hard woods without fear of splitting the wooden members,and further, the teeth must not cut excessive amounts of the woodfibers-thus reducing the effective strength of the structural memberbelow the effective strength of the connector plate.

It is therefore an object of the present invention to provide anapproved connector plate in which the tooth design and orientation eachcontribute to an improved yield strength.

It is another object of the present invention to provide a connectorplate, as above, in which the teeth provide an improved entryi.e., theteeth may be set into the wooden members with modest embedment pressurewithout cutting excessive fibers, without splitting the wooden membersand without themselves bending or crushing during embedment.

It is still another object of the present invention to provide aconnector plate, as above, in which the teeth have an exceptionally highaggregate shear strength.

It is a further object of the present invention to provide a connectorplate, as above, in which the teeth provide an increase in the linealpenetration for a given plate area, thus directly increasing the holdingpower.

It is a still further object ofthe present invention to provide aconnector plate, as above, which has exceptional tensile strength whenused on tensile joints and, at the same time, exceptional shear strengthwhen used on shear joints.

It is an even further object of the present invention to provide aconnector plate, as above, in which the configuration and orientation ofthe teeth are such as to provide an exceptionally desirableslip-to-failure ratio and also to provide a reduction of the waste metalfrom which the plates are fabricated.

Additionally, it is an object of the present invention to provide aconnector plate, as above, which has an increased ultimate strength aswell as yield strength to permit a higher design strength value than anyknown prior are construction.

These and other objects which will become apparent from the followingspecification are accomplished by means hereinafter described andclaimed.

One preferred embodiment of the plate with a preferred and alternatetooth construction, is shown by way of example in the accompanyingdrawings and hereinafter described in detail without attempting to showall of the various forms and modifications in which the invention mightbe embodied; the invention being measured by the appended claim and notby the details of the specification.

In the drawings:

FIG. 1 is an elevation of a typical truss joint depicting a connectorplate according to the concept of the present invention in top plan;

FIG. 2 is an enlarged bottom plan of the connector plate shown in FIG. 1and taken substantially on line 22 of FIG. 3;

FIG. 3 is an enlarged cross section taken substantially on line 3-3 ofFIG. 1;

FIG. 4 is a cross section taken substantially on line 44 of FIG. 2showing the teeth in elevation;

FIG. 5 is an enlarged area of FIG. 4;

FIG. 6 is a side elevation taken substantially on line 66 of FIG. 5;

FIG. 7 is a cross section taken substantially on line 7--7 of FIG. 5;

FIG. 8 is a partial top plan showing how the end rows of teeth onsuccessively struck plates can be formed from the common wastetherebetween;

FIG. 9 is a view similar to FIG. depicting an alternate toothconstruction; and,

FIG. 10 is a view similar to FIG. 8 depicting the interfitting of theteeth shown in FIG. 9.

In general, a connector plate constructed according to the concept ofthe present invention has a plurality of teeth which extend transverselyoutwardly of the plate from which they are struck, or punched. Eachtooth is preferably dished and has a generally rectangular base portionand a narrower rectangular tip portion. The outermost end of the tipportion as well as the shoulder by which the lesser width of the tipportion is offset from the base portion are, for the best results,sharpened. The teeth may be positioned in a particular fashion on eachside of the medial portion of the plate which is adapted to overlie, orspan, the joinder line of the Wooden members joined thereby to obtaincertain reuslts. Specifically, the teeth are particularly oriented tostand between the medial portion and the openings from which they arestruck to increase the yield strength. Further, the teeth may alsopreferably be located in rows parallel to, and on each side of, themedial portion with the first row of teeth on each side of the medialportion having lesser teeth than the more remote row, or rows toincrease the tensile strength of the plate.

Referring more particularly to the drawings, a connector plate accordingto the present invention, and designated generally by the numeral 16, isdepicted connecting the lower chord member 11 to the kingpost 12 of whatmay be a tensile joint of a wooden truss. Generally, a plate 10 isapplied to each side of the joint.

The teeth, indicated generally by the numeral 13, which are embeded intothe mooden members 11 and 12 are best seen in FIGS. 3, 4, 5, 6 and 7 andare punched individually from the plate, leaving a hole 14 of the sameconfiguration as the outline of the tooth.

Each tooth 13 has a thickness generally equal to the thickness of theplate because it was struck therefrom, and each tooth has a base portion15 the side edges 16 and 17 of which are generally parallel and extendperpendicularly outwardly from the plate. A tip portion 18 having alesser width than the base portion 15 is formed integrally outwardlythereof with one edge 16A being preferably a continuation of edge 16 ofthe base portion 15, and a second edge 19 parallel thereto but spacedcloser to edge 16A than the corresponding edge 17 of the base portion 15is spaced to edge 16. Edges 17 and H are joined by a shoulder 20. Theshoulder 20 may be inclined if deemed necessary to facilitate entry intothe wood, but may also be squared-off, or parallel to the plane of theplate, as is the shoulder 26A, 0n the tooth 13 shown in FIG. 9.

The preferred proportions of the teeth can best be seen in FIGS. 5 and9. The width of the base portion 15 is approximately one-quarter thelength of the tooth 13, or 13', with the length of the base portion 15being approximately /2 to the length of the tooth, and the width of thetip portion 18 being approximately /2 the width of the base portion 15.Applying these preferred proportions to obtain dimensions for a typicaltooth constructed according to the concept of this invention, a tooth /2of an inch in length would have a base portion /8 of an inch in widthand approximately of an inch long with the width of the tip portionbeing approximately of an inch.

Continuing with the example of the tooth size described above, a typicalconnector plate, say a plate sufficient for joining two two by fours andwhich could be fabricated from 16-20 gauge metal measuring 3" by 5",would have a medial portion 21 adapted to span the joinder line, i.e.,the abutment of the end 22 of the king post 12 to the lower chord member11. A plurality of teeth 13 punched individually from such a plate oneach side of the medial portion 21 leave a plurality of openings 14 inthe plate from which the teeth 13 were punched, or struck.

Each tooth 13 extends perpendicularly outwardly from the plate with thebroadest extent of the base portion 15 generally parallel to the medialportion 21 so that each tooth provides a large area near the surface ofthe Wood transversely of the joinder line where most of the force acrossthe joint is transferred between the plate and the wooden members.Because the majority of this force transmission is applied near thesurface of the wooden members it can be seen that only the base portion15 need have the maximum width. The lesser width of the tip portion thuspermitted does not alter the overall penetration of the tooth and theholding power incident thereto, and, at the same time, results in easierentry of the tooth into the wood by dividing the resistance offered bythe wood against entry of the teeth over two layers of the wood fibers.The entry of the tooth can thus be considered as a two-stage operationwhich has been found to require a lesser total force to accomplishembedment without adversely affecting the holding power of the teeth.

This lower embedment pressure is also enhanced by sharpening both theoutermost end 24 of the tip portion 18 and the shoulder 20, as bybeveling the edges transversely the broadest dimension of the tooth asshown in FIG. 6.

By sharpening both the end 24 of the tip portion 18 and the shoulder 29,the embedment of the tooth is cleanly accomplished with the minimumtearing and crushing of the wooden fibers. This has been found not onlyto lower the embedment pressure but also to reduce the tendency of thewood to split and has even proved to increase the yield point andultimate strength of the plate.

It must be noted that each tooth is dished away from the joinder line,or medial portion 21 of the plate. Each tooth 13 is dished from theoutermost end, or tip, 24 along its entire length to the root 25. Thisparticular dishing of the tooth not only strengthens the tooth towithstand the embedrnent pressure without bending, but also provides aradius at the root 13 which forces the fibe s at that point toward thejoinder line to put them initially in compression against the tooth.Moreover, with the edges of the dished tooth oriented away from thiscompressed portion of the wood the application of a lateral load on thetooth which would tend to move it toward the joinder line, does notcause the edges of the tooth to cut the fibers which, it has been found,markedly decreases the yield point strength of teeth oriented reversely.

Also with regard to the positioning of the teeth, it should be observedthat the teeth 13 are all particularly positioned to stand between theopening 14 from which they were struck and the joinder line, or medialportion 21 of the plate. This location facilitates imparting therequired dishing of the teeth described above, but more important italso increases the tensile strength of the plate. As can be seen fromFIG. 1 the entire cross section of the plate is available for tensilestrength across the joinder line and between the first row of teeth oneither side thereof, i.e., rows A and B, respectively. The teeth inthese first rows A and B actually transfer a portion of the load betweenthe plate and the wood before the effective cross section of the plateis reduced by the openings 14. To further increase the tensile strengthof the connector plate a lesser number of teeth are utilized in thefirst row of teeth, A and B, one each side of the medial portion 21 thanin the second row C and D, respectively. In the example depicted, rows Aand B contain approximately half the number of teeth contained in therows next remote from the medial por tion 21.

The lesser number of teeth in the first rows A and B also further reducethe tendency of the ends of the wooden members to split or be crushed asloads are applied. Furthermore, accidental misalignment of the platewith the joint is far less critical than with known prior art connectorplates wherein a severe loss of tensile strength of the joint can beoccasioned merely by a slight accidental lateral misplacement of theplate with respect to the joinder line.

In addition to the increased yield strength occasioned by positioningthe teeth 13 between the medial portion 21 of the plate and the openings14 from which the teeth are struck, this placement has been found topermit a metal savings of as much as 7 percent in the fabrication ofconnector plates suitable for joining structural members made from twoby four dimensional lumber. This savings is accomplished by punching themost remote row of teethrows E and F as shown, which preferably have thesame number of teeth as rows C and Don each end of the plate at leastpartially out of the same metal stock from which the end row of teeth onthe next plate were punched. One way in which this interpositioning ofthe teeth to be formed can be laid out is shown by way of example inFIG. 8 wherein the teeth 13 on plate 10 are shown interpositioned withteeth 13A of plate 10A. This layout requires a spacing between teeth tobe equal to the width of the base portion of each tooth, and the span ofthe side rails 26 and 27 to be of unequal Width and reversed. Note 26Aand 27, on successive plates. Other similar interrelationships can beobtained by placement of the teeth shoulder-to-shoulder should thespacing between teeth be desired to be less than the width of the baseportion of the tooth or should it be desired to make the side rails ofequal width. This arrangement is shown in FIG. 10 Where teeth 13' areinterlocked shoulder 20A to shoulder 20A between successive plates 10Cand 10D.

It should thus be apparent that a connector plate constructed with theteeth shaped and oriented according to the concept of the presentinvention provide improved yield and ultimate strengths, require lowerembedment pressures, and otherwise accomplish the objects of theinvention.

I claim:

1. A connector plate for joining wooden members, said plate having aplurality of teeth, said teeth extending transversely outwardly fromsaid plate, each said tooth having a thickness substantially the same asthe thick ness of the plate, each said tooth having a base portion and atip portion, said base portion having edges extending perpendicularlyfrom said plate in parallel relation, said tip portion also havingparallel edges oriented perpendicularly of said plate, one of the edgesof said tip portion being a continuation of one edge of said baseportion, the other edge of said tip portion being offset from thecorresponding edge of said base portion and connected thereto by ashoulder so that said nip portion is approximately one-half the width ofsaid base portion, said shoulder being located approximately onehalf tothree-quarters of the length of the tooth outwardly from the plate, saidtooth being dished along substantially its entire length, the free endof said tip portion and said shoulder being sharp so as to readilypenetrate the wooden members with a minimum tearing of the wood fibers.References Cited UNITED STATES PATENTS 1,921,194 8/1933 Kelly -303,068,738 12/1962 Nulick 85-13 3,225,643 12/1965 Couch 85-13 3,266,3628/1966 Carr 8513 CARL W. TOMLIN, Primary Examiner.

RAMON S. BRITTS, Assistant Examiner.

